1. Field of the Invention
The present invention relates to disk drive apparatuses such as a magnetic disk drive including a disk which rotates at high speed.
2. Description of the Related Art
In general, a magnetic disk apparatus includes a case in which are provided a magnetic disk, a spindle motor which supports and rotates the magnetic disk, a carriage assembly supporting a magnetic head, a voice coil motor which drives the carriage assembly, and a substrate unit.
The spindle motor includes a cylindrical hub, and a plurality of magnetic disks and spacer rings are alternately stacked on the hub. Moreover, these magnetic disks and spacer rings are fixed onto the outer periphery of the hub by a disk damper attached to a tip end of the hub.
In this magnetic disk apparatus, the number of revolutions of the magnetic disk needs to be raised in order to carry out high-speed data processing. In recent years, a high-speed rotating type magnetic disk apparatus has been researched. However, when the magnetic disk rotates at high speed, an air current is generated in the same rotation direction as that of the magnetic disk. Turbulence of the air current causes a phenomenon called disk flutter in which the magnetic disk vibrates. In this case, positioning precision of the magnetic head with respect to the magnetic disk drops, and a problem is generated in enhancing recording density.
To solve the above-described problem, according to the magnetic disk apparatus disclosed, for example, in Jpn. Pat. Appln. KOKAI Publication No. 10-162548, a circulatory current channel is formed to generate a forced current toward the outer periphery from an inner periphery during the rotation of a magnetic disk, and the turbulence of the air current is suppressed in order to reduce the disk flutter.
In the magnetic disk apparatus, a method for forming the circulatory channel comprises: processing cutouts or taper portions for passing air in the hub and spacer of the spindle motor; and additionally forming an air introduction channel for introducing the air current into these cutouts or taper portions in the base and top cover of the magnetic disk apparatus.
However, in the magnetic disk apparatus which requires a high recording density, processing precisions of components directly influence an apparatus capability. Therefore, when the individual components are processed to form the circulatory channel, increases of processing and finishing costs cannot be avoided with the increase of the number of portions to be processed.
In order to prevent the disk flutter, a magnetic disk apparatus has also been proposed in which the shape of the top cover is changed or another component is disposed. However, any apparatus has many problems to be solved such as substantial change in a shape, increase in the number of components, and securing of assembly precision.